Wnt4 inhibits cell motility induced by oncogenic Ras

Mutation analysis of WNT4 gene in SRY negative 46,XX DSD patients with Mullerian agenesis and/or gonadal dysgenesis- An Indian study

Developmental disruption of the Mullerian duct and gonads in females leads to Mullerian agenesis and gonadal dysgenesis, respectively. These two structural abnormalities are coming under the 46,XX DSD (Disorders of Sexual Development) classification, the majority of cases the aetiology remains elusive. Without the SRY gene, WNT4 plays a key role in female reproductive structure development. Since there are no studies that explored the involvement of the WNT4 gene in Indian 46,XX DSD patients, we analysed the role of WNT4 in Indian 46,XX DSD patients with Mullerian agenesis and/or Gonadal dysgenesis. In our study, we recruited 103 adolescent girls with primary amenorrhea. After the cytogenetic and SRY gene analysis, we included thirty-two 46,XX DSD patients with Mullerian agenesis and/or gonadal dysgenesis for WNT4 gene mutation analysis. PCR sequencing was performed for all the coding exons of the WNT4 gene. Bioinformatic tools like Mutation Taster, Human Splicing Finder, and miRDB were used. We observed single nucleotide variations in three patients. One patient showed a known synonymous polymorphism (c.861C > T; p.G287G, rs544988174). miRDB data revealed the absence of microRNA regulatory sites in this region. The other two cases carried a nucleotide substitution in intronic regions and did not affect the normal splicing mechanism. In conclusion, we could not find any indication about WNT4 involvement in the disease condition. In the future, WNT4 promoter analysis in these patients and molecular characterization of the WNT4 coding and promoter region in more patients are needed to link WNT4 variants with these structural abnormalities.

A ceRNA Circuitry Involving the Long Noncoding RNA Klhl14-AS, Pax8, and Bcl2 Drives Thyroid Carcinogenesis

Klhl14-AS is a long noncoding RNA expressed since early specification of thyroid bud and is the most enriched gene in the mouse thyroid primordium at E10.5. Here, we studied its involvement in thyroid carcinogenesis by analyzing its expression in cancer tissues and different models of neoplastic transformation. Compared with normal thyroid tissue and cells, Klhl14-AS was significantly downregulated in human thyroid carcinoma tissue specimens, particularly the anaplastic histotype, thyroid cancer cell lines, and rodent models of thyroid cancer. Downregulating the expression of Klhl14-AS in normal thyroid cells decreased the expression of thyroid differentiation markers and cell death and increased cell viability. These effects were mediated by the binding of Klhl14-AS to two miRNAs, Mir182-5p and Mir20a-5p, which silenced Pax8 and Bcl2, both essential players of thyroid differentiation. MIR182-5p and MIR20a-5p were upregulated in human thyroid cancer and thyroid cancer experimental models and their effects on Pax8 and Bcl2 were rescued by Klhl14-AS overexpression, confirming Klhl14-AS as a ceRNA for both Pax8 and Bcl2. This work connects deregulation of differentiation with increased proliferation and survival in thyroid neoplastic cells and highlights a novel ceRNA circuitry involving key regulators of thyroid physiology. SIGNIFICANCE: This study describes a new ceRNA with potential tumor suppression activity and helps us better understand the regulatory mechanisms during thyroid differentiation and carcinogenesis.

Dual Oncogenic/Anti-Oncogenic Role of PATZ1 in FRTL5 Rat Thyroid Cells Transformed by the Ha-RasV12 Oncogene

PATZ1 is a transcriptional factor downregulated in thyroid cancer whose re-expression in thyroid cancer cells leads to a partial reversion of the malignant phenotype, including the capacity to proliferate, migrate, and undergo epithelial-to-mesenchymal transition. We have recently shown that PATZ1 is specifically downregulated downstream of the Ras oncogenic signaling through miR-29b, and that restoration of PATZ1 in Ha-Ras transformed FRTL5 rat thyroid cells is able to inhibit their capacities to proliferate and migrate in vitro. Here, we analyzed the impact of PATZ1 expression on the in vivo tumorigenesis of these cells. Surprisingly, FRTL5-Ras-PATZ1 cells showed enhanced tumor initiation when engrafted in nude mice, even if their tumor growth rate was reduced compared to that of FRTL5-Ras control cells. To further investigate the cause of the enhanced tumor engraftment of FRTL5-Ras-PATZ1 cells, we analyzed the stem-like potential of these cells through their capacity to grow as thyrospheres. The results showed that restoration of PATZ1 expression in these cells increases stem cell markers’ expression and self-renewal ability of the thyrospheres while limiting their growth capacity. Therefore, we suggest that PATZ1 may play a role in enhancing the stem cell potential of thyroid cancer cells, but, at the same time, it impairs the proliferation of non-stem cells.

A Toxicogenomic Approach Reveals a Novel Gene Regulatory Network Active in In Vitro and In Vivo Models of Thyroid Carcinogenesis

Epidemiological and experimental studies emphasize the link between environmental chemicals exposure and thyroid cancer. However, this association is strongly debated and the mechanisms of action of environmental thyroid carcinogens still need to be identified. The analysis of in vitro transcriptomic data developed to investigate the effects of chlorpyrifos on immortalized thyrocytes highlighted the impaired expression of genes involved in endodermal carcinogenesis. This endodermal carcinogenic gene-network (ECGN, including Zfp36l2, Dmbt1, Ddit4), was validated in cellular and mouse models of thyroid carcinogenesis, characterized by the constitutive activation of the mitogen-activated protein kinase (MAPK) pathway and in immortalized thyrocytes exposed to tetrachlorodibenzo-p-dioxin (TCDD) and chlorpyrifos (CPF). The mRNA levels of Zfp36l2, Dmbt1 and Ddit4 were increased in models characterized by MAPK activation or following TCDD exposure, whereas they were inhibited by CPF exposure. Overall, the ECGN transcripts identify a novel gene-regulatory network associated with thyroid carcinogenesis promoted by genetic mutation or by environmental carcinogens. The latter have opposite effects on the modulation of the ECGN transcripts according to their mechanisms of action in promoting carcinogenesis. Therefore, the analyses of ECGN might be helpful in discriminating compounds that promote cellular survival associated or not to proliferation of thyrocytes.

Relationship of WNT4 Gene with the Risk of Epithelial Ovarian Cancer: A Han Chinese Population-Based Association Study

OBJECTIVE

In China, epithelial ovarian cancer (EOC) patients account for the majority of ovarian cancer patients. The pathogenesis of EOC, one of the most lethal gynecological malignancies, remains unclear. Recently, the role of WNT4 in gynecological disease and tumor development was reported, and a suspicious association of WNT4 with EOC was identified in Europeans. However, the contributions of the WNT4 gene to EOC and the underlying molecular mechanisms remains largely unknown. To determine whether the WNT4 gene is associated with EOC, this study investigated polymorphisms of the WNT4 gene in Han Chinese individuals.

MATERIALS AND METHODS

We designed a case/control study with 707 EOC patients and 1563 unrelated healthy controls of Han Chinese descent. A total of eight tag single-nucleotide polymorphisms (SNPs) were genotyped successfully, and both single SNP and haplotype analyses were performed to detect the potential association of variations in the WNT4 gene with EOC.

RESULTS

The SNP rs56318008 was found to be strongly associated with EOC risk. In the serous EOC subgroup, individuals harboring the T allele of rs56318008 exhibited a higher risk of EOC than individuals harboring the C allele. Moreover, the odds ratios and 95% confidence intervals revealed an increased risk of EOC in individuals with the T allele of the SNP, and haplotypic analyses confirmed the results, showing a similar pattern.

CONCLUSION

Our results show that the WNT4 gene is associated with EOC risk, indicating that this gene may be a potential genetic risk factor for developing EOC.

Wnt Signaling in Thyroid Homeostasis and Carcinogenesis

The Wnt pathway is essential for stem cell maintenance, but little is known about its role in thyroid hormone signaling and thyroid stem cell survival and maintenance. In addition, the role of Wnt signaling in thyroid cancer progenitor cells is also unclear. Here, we present emerging evidence for the role of Wnt signaling in somatic thyroid stem cell and thyroid cancer stem cell function. An improved understanding of the role of Wnt signaling in thyroid physiology and carcinogenesis is essential for improving both thyroid disease diagnostics and therapeutics.

Tissue- and Cell Type-Specific Expression of the Long Noncoding RNA Klhl14-AS in Mouse

lncRNAs are acquiring increasing relevance as regulators in a wide spectrum of biological processes. The extreme heterogeneity in the mechanisms of action of these molecules, however, makes them very difficult to study, especially regarding their molecular function. A novel lncRNA has been recently identified as the most enriched transcript in mouse developing thyroid. Due to its genomic localization antisense to the protein-encoding Klhl14 gene, we named it Klhl14-AS. In this paper, we highlight that mouse Klhl14-AS produces at least five splicing variants, some of which have not been previously described. Klhl14-AS is expressed with a peculiar pattern, characterized by diverse relative abundance of its isoforms in different mouse tissues. We examine the whole expression level of Klhl14-AS in a panel of adult mouse tissues, showing that it is expressed in the thyroid, lung, kidney, testis, ovary, brain, and spleen, although at different levels. In situ hybridization analysis reveals that, in the context of each organ, Klhl14-AS shows a cell type-specific expression. Interestingly, databases report a similar expression profile for human Klhl14-AS. Our observations suggest that this lncRNA could play cell type-specific roles in several organs and pave the way for functional characterization of this gene in appropriate biological contexts.

Approaches for targeting cancer stem cells drug resistance

INTRODUCTION

Several reports have suggested that a population of undifferentiated cells known as cancer stem cells (CSCs), is responsible for cancer formation and maintenance. In the last decade, the presence of CSCs in solid cancers have been reported. Areas covered: This review summarizes the main approaches for targeting CSCs drug resistance. It is indeed known that CSCs may contribute to resistance to conventional chemotherapy, radiotherapy and targeted agents. Among the mechanisms by which CSCs escape anticancer therapies, removal of therapeutic agents by drug efflux pumps, enhanced DNA damage repair, activation of mitogenic/anti-apoptotic pathways; the main features of CSCs, stemness and EMT, are involved, as well as the capability to evade immune response. Expert opinion: Different approaches are suitable to target CSCs mediated drug resistance. Some of them are currently under clinical evaluation in different cancer types. A better understanding of CSC biology, as well as more accurate study design, may maximize the therapeutic effects of these agents. In this respect, it is important to establish: (i) which molecules should be targeted; (ii) what drug combinations may be suitable; (iii) which patient settings will CSC targeting offer the highest clinical benefit; and (iv) how to integrate therapeutic approaches targeting CSCs with standard cancer therapy.

WNT4 mediates the autocrine effects of growth hormone in mammary carcinoma cells

The expression of Wingless and Int-related protein (Wnt) ligands is aberrantly high in human breast cancer. We report here that WNT4 is significantly upregulated at the mRNA and protein level in mammary carcinoma cells expressing autocrine human growth hormone (hGH). Depletion of WNT4 using small interfering (si) RNA markedly decreased the rate of human breast cancer cell proliferation induced by autocrine hGH. Forced expression of WNT4 in the nonmalignant human mammary epithelial cell line MCF-12A stimulated cell proliferation in low and normal serum conditions, enhanced cell survival and promoted anchorage-independent growth and colony formation in soft agar. The effects of sustained production of WNT4 were concomitant with upregulation of proliferative markers (c-Myc, Cyclin D1), the survival marker BCL-XL, the putative WNT4 receptor FZD6 and activation of ERK1 and STAT3. Forced expression of WNT4 resulted in phenotypic conversion of MCF-12A cells, such that they exhibited the molecular and morphological characteristics of mesenchymal cells with increased cell motility. WNT4 production resulted in increased mesenchymal and cytoskeletal remodeling markers, promoted actin cytoskeleton reorganization and led to dissolution of cell-cell contacts. In xenograft studies, tumors with autocrine hGH expressed higher levels of WNT4 and FZD6 when compared with control tumors. In addition, Oncomine data indicated that WNT4 expression is increased in neoplastic compared with normal human breast tissue. Accordingly, immunohistochemical detection of WNT4 in human breast cancer biopsies revealed higher expression in tumor tissue vs normal breast epithelium. WNT4 is thus an autocrine hGH-regulated gene involved in the growth and development of the tumorigenic phenotype.

PATZ1 is a target of miR-29b that is induced by Ha-Ras oncogene in rat thyroid cells

The regulatory transcriptional factor PATZ1 is constantly downregulated in human thyroid cancer where it acts as a tumour suppressor by targeting p53-dependent genes involved in Epithelial-Mesenchymal Transition and cell migration. The aim of the present work was to elucidate the upstream signalling mechanisms regulating PATZ1 expression in thyroid cancer cells. The bioinformatics search for microRNAs able to potentially target PATZ1 led to the identification of several miRNAs. Among them we focused on the miR-29b since it was found upregulated in rat thyroid differentiated cells transformed by the Ha-Ras oncogene towards a high proliferating and high migratory phenotype resembling that of anaplastic carcinomas. Functional assays confirmed PATZ1 as a target of miR-29b, and, consistently, an inverse correlation between miR-29b and PATZ1 protein levels was found upon induction of Ha-Ras oncogene expression in these cells. Interestingly, restoration of PATZ1 expression in rat thyroid cells stably expressing the Ha-Ras oncogene decreased cell proliferation and migration, indicating a key role of PATZ1 in Ras-driven thyroid transformation. Together, these results suggest a novel mechanism regulating PATZ1 expression based on the upregulation of miR-29b expression induced by Ras oncogene.

microRNA regulation of Wnt signaling pathways in development and disease

Wnt signaling pathways and microRNAs (miRNAs) are critical regulators of development. Aberrant Wnt signaling pathways and miRNA levels lead to developmental defects and diverse human pathologies including but not limited to cancer. Wnt signaling pathways regulate a plethora of cellular processes during embryonic development and maintain homeostasis of adult tissues. A majority of Wnt signaling components are regulated by miRNAs which are small noncoding RNAs that are expressed in both animals and plants. In animal cells, miRNAs fine tune gene expression by pairing primarily to the 3'untranslated region of protein coding mRNAs to repress target mRNA translation and/or induce target degradation. miRNA-mediated regulation of signaling transduction pathways is important in modulating dose-sensitive response of cells to signaling molecules. This review discusses components of the Wnt signaling pathways that are regulated by miRNAs in the context of development and diseases. A fundamental understanding of miRNA functions in Wnt signaling transduction pathways may yield new insight into crosstalks of regulatory mechanisms essential for development and disease pathophysiology leading to novel therapeutics.

Pax8 modulates the expression of Wnt4 that is necessary for the maintenance of the epithelial phenotype of thyroid cells

Background

The transcription factor Pax8 is expressed during thyroid development and is involved in the morphogenesis of the thyroid gland and maintenance of the differentiated phenotype. In particular, Pax8 has been shown to regulate genes that are considered markers of thyroid differentiation. Recently, the analysis of the gene expression profile of FRTL-5 differentiated thyroid cells after the silencing of Pax8 identified Wnt4 as a novel target. Like the other members of the Wnt family, Wnt4 has been implicated in several developmental processes including regulation of cell fate and patterning during embryogenesis. To date, the only evidence on Wnt4 in thyroid concerns its down-regulation necessary for the progression of thyroid epithelial tumors.

Results

Here we demonstrate that Pax8 is involved in the transcriptional modulation of Wnt4 gene expression directly binding to its 5’-flanking region, and that Wnt4 expression in FRTL-5 cells is TSH-dependent. Interestingly, we also show that in thyroid cells a reduced expression of Wnt4 correlates with the alteration of the epithelial phenotype and that the overexpression of Wnt4 in thyroid cancer cells is able to inhibit cellular migration.

Conclusions

We have identified and characterized a functional Pax8 binding site in the 5’-flanking region of the Wnt4 gene and we show that Pax8 modulates the expression of Wnt4 in thyroid cells. Taken together, our results suggest that in thyroid cells Wnt4 expression correlates with the integrity of the epithelial phenotype and is reduced when this integrity is perturbed. In the end, we would like to suggest that the overexpression of Wnt4 in thyroid cancer cells is able to revert the mesenchymal phenotype.

Genetic variants of the Wnt signaling pathway as predictors of recurrence and survival in early-stage non-small cell lung cancer patients

Early-stage non-small cell lung cancer (NSCLC) is potentially curative. Nevertheless, many patients will show disease recurrence after curative treatment. The Wnt signaling pathway is a developmental and stem cell pathway that plays an important role in tumorigenesis and may affect cancer progression. We hypothesize that genetic variants of the Wnt pathway may influence clinical outcome in early-stage NSCLC patients. We genotyped 441 functional and tagging single nucleotide polymorphisms (SNPs) from 54 genes of the Wnt pathway in 535 early-stage NSCLC patients treated with curative intent therapy including surgery and chemotherapy. For validation, 4 top SNPs were genotyped in 301 early-stage NSCLC patients from the Mayo Clinic. Cox proportional hazard model and combined SNP analyses were performed to identify significant SNPs correlated with recurrence-free and overall survival. Results from discovery group showed a total of 40 SNPs in 20 genes correlated with disease recurrence (P < 0.05). After correction for multiple comparisons, rs2536182 near Wnt16 remained significant (q < 0.1), which was validated in the replication population. Thirty-nine SNPs in 16 genes correlated with overall survival (P < 0.05) in the discovery group, and seven remained significant after multiple comparisons were considered (q < 0.1). In patients receiving surgery-only treatment, rs10898563 of FZD4 gene was associated with both recurrence-free and overall survival. Joint SNP analyses identified predictive markers for recurrence stratified by treatment. Our findings suggest inherited genetic variation in the Wnt signaling pathway may contribute to variable clinical outcomes for patients with early-stage NSCLC.

Restoration of WNT4 inhibits cell growth in leukemia-derived cell lines

Background

WNT signaling pathways are significantly altered during cancer development. Vertebrates possess two classes of WNT signaling pathways: the “canonical” WNT/β-catenin signaling pathway, and the “non-canonical” pathways including WNT/Ca2⁺ and WNT/Planar cell polarity [PCP] signaling. WNT4 influences hematopoietic progenitor cell expansion and survival; however, WNT4 function in cancer development and the resulting implications for oncogenesis are poorly understood.

The aim of this study was twofold: first, to determine the expression of WNT4 in mature peripheral blood cells and diverse leukemia-derived cells including cell lines from hematopoietic neoplasms and cells from patients with leukemia; second, to identify the effect of this ligand on the proliferation and apoptosis of the blast-derived cell lines BJAB, Jurkat, CEM, K562, and HL60.

Methods

We determined WNT4 expression by quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) in peripheral blood mononuclear cells (PBMCs) and T- and B-lymphocytes from healthy individuals, as well as from five leukemia-derived cell lines and blasts derived from patients with leukemia. To analyze the effect of WNT4 on cell proliferation, PBMCs and cell lines were exposed to a commercially available WNT4 recombinant human protein. Furthermore, WNT4 expression was restored in BJAB cells using an inducible lentiviral expression system. Cell viability and proliferation were measured by the addition of WST-1 to cell cultures and counting cells; in addition, the progression of the cell cycle and the amount of apoptosis were analyzed in the absence or presence of WNT4. Finally, the expression of WNT-pathway target genes was measured by qRT-PCR.

Results

WNT4 expression was severely reduced in leukemia-derived cell lines and blasts derived from patients with leukemia. The exposure of cell lines to WNT4 recombinant protein significantly inhibited cell proliferation; inducing WNT4 expression in BJAB cells corroborated this observation. Interestingly, restoration of WNT4 expression in BJAB cells increased the accumulation of cells in G1 phase, and did not induce activation of canonical WNT/β-catenin target genes.

Conclusions

Our findings suggest that the WNT4 ligand plays a role in regulating the cell growth of leukemia-derived cells by arresting cells in the G1 cell cycle phase in an FZD6-independent manner, possibly through antagonizing the canonical WNT/β-catenin signaling pathway.

Expression profile and function of Wnt signaling mechanisms in malignant mesothelioma cells

Malignant mesothelioma (MM) is an uncommon and particularly aggressive cancer associated with asbestos exposure, which currently presents an intractable clinical challenge. Wnt signaling has been reported to play a role in the neoplastic properties of mesothelioma cells but has not been investigated in detail in this cancer. We surveyed expression of Wnts, their receptors, and other key molecules in this pathway in well established in vitro mesothelioma models in comparison with primary mesothelial cultures. We also tested the biological response of MM cell lines to exogenous Wnt and secreted regulators, as well as targeting β-catenin. We detected frequent expression of Wnt3 and Wnt5a, as well as Fzd 2, 4 and 6. The mRNA of Wnt4, Fzd3, sFRP4, APC and axin2 were downregulated in MM relative to mesothelial cells while LEF1 was overexpressed in MM. Functionally, we observed that Wnt3a stimulated MM proliferation while sFRP4 was inhibitory. Furthermore, directly targeting β-catenin expression could sensitise MM cells to cytotoxic drugs. These results provide evidence for altered expression of a number of Wnt/Fzd signaling molecules in MM. Modulation of Wnt signaling in MM may prove a means of targeting proliferation and drug resistance in this cancer.

Avian WNT4 in the female reproductive tracts: potential role of oviduct development and ovarian carcinogenesis

The wingless-type MMTV integration site family of proteins (WNTs) is highly conserved secreted lipid-modified signaling molecules that play a variety of pivotal roles in developmental events such as embryogenesis, tissue homeostasis and cell polarity. Although, of these proteins, WNT4 is known to be involved in genital development in fetuses of mammalian species, its role is unknown in avian species. Therefore, in this study, we investigated expression profiles, as well as hormonal and post-transcriptional regulation of WNT4 expression in the reproductive tract of female chickens. Results of this study demonstrated that WNT4 is most abundant in the stromal and luminal epithelial cells of the isthmus and shell gland of the oviduct, respectively. WNT4 is also most abundant in the glandular epithelium of the shell gland of the oviduct of laying hens at 3 h post-ovulation during the laying cycle. In addition, treatment of young chicks with diethylstilbestrol (DES, a synthetic estrogen agonist) stimulated WNT4 only in the glandular epithelial cells of the isthmus and shell gland of the oviduct. Moreover, results of our study demonstrated that miR-1786 influences WNT4 expression via specific binding sites in its 3'-UTR. On the other hand, our results also indicate that WNT4 is expressed predominantly in the glandular epithelium of cancerous ovaries, but not in normal ovaries of hens. Collectively, these results indicate cell-specific expression of WNT4 in the reproductive tract of chickens and that it likely has crucial roles in development and function of oviduct as well as initiation of ovarian carcinogenesis in laying hens.